1. Field of Invention
The present invention generally relates to an electrical connector applied to transmit electrical signals, and more particularly relates to an electrical connector which can reduce the return loss caused by reflections in the communication system, enhance transmission performance, and meet the EIA/TIA, Category 5e, standard.
2. Related Art
Information transmissions through network communication are recently more and more popular. The applications are getting wider. As a demand, the high speed and high efficiency transmissions require high quality cabling and connectors. Generally, the network communication paths are composed of transmission media and electrical connectors. On the transmission media, there are twisted pair cables, coaxial cables, and optical fibers. Certain defects occur in the communication path which will worsen as the frequency of signals gets higher. The defects may come from:
1) attenuation of signal. The level of signal decreases when the transmission distance increases;
2) cross talk, which is induced by electromagnetic interference between closely spaced cables or contacts; and
3) return loss, which is caused by reflections in the communication system due to the discontinuous impedance.
Taking unshielded twisted pair (UPT) cabling for example, the cable includes two isolated copper wires twisted with a certain pitch and a certain manner. A pair or two pairs of twisted cables constitute a communication chain as a simplest transmission medium. The twisted pairs are commonly used in computer communication networks. But, in their connecting hardware, cross talk is induced due to capacitive and inductive couplings between adjacent conductors. As the frequency of the signal increases, the magnitude of the cross talk is especially increased logarithmically, and the impedance also increases, which badly distort the high frequency signals.
For the aforesaid reasons, the EIA/TIA 568 standard established by Electronic Industries Association has been adopted into IEEE 802.3 u standard by the Institute of Electrical and Electronics Engineers, Inc. The IEEE 802.3 u standard includes all the standards for the transmission medium and connectors, and classifies them into several categories.
For example, xe2x80x9cCategory 3xe2x80x9d are network cabling for voice which use solid copper wires of 24 AWG with impedance 100xcexa9 and certifies UTP for data transmission up to 10 Mbps; xe2x80x9cCategory 4xe2x80x9d are the same as Category 3 but with data transmission up to 16 Mbps; xe2x80x9cCategory 5xe2x80x9d are the same as Category 3 but with data transmission up to 10 Mbps. Another category with tighter requirements than Category 5 is xe2x80x9cCategory 5exe2x80x9d which requests for a limited extent of return loss caused by reflections in the communication system due to the discontinuous impedance. The following tables A and B are standards of maximum return loss for cable and for connectors according to the EIA/TIA Category 5e standard.
An exploded view of a unitary electrical connector of prior arts is shown in FIG. 1. The electrical connector mainly includes a case 10, a wiring base 12, a plurality of contacts 20 and a bottom piece 13. One end of the case 10 is formed with a wiring portion 16, while the other end is a socket 18 for terminal plug of communication wires. The plurality of contacts 20 are fixed by the wiring base 12 and the bottom piece 13, and engaged into the wiring portion 16 to be a composed unit in the case 10. Each of the contacts 20 is a metallic member 22 having one end 23 sharply bent and inserted into socket 18 as contacts; and the other end 28 bent with a right angle and formed as a fork for receiving a communication wire. Some of the members 22 are formed with holes 24 to be engaged with extrusions 26 formed on the bottom piece 13 and fixed by the wiring base 12 and the bottom piece 13. Each of the forks is a slot with an expended opening and a round end for receiving and fixing the unshown communication wire.
The wiring base 12 is made of electrically isolative material and formed with a plurality of wire guides 121 and separated slots 122 in the middle of the guides 121 for fixing the fork ends 28 of the contacts 20 therein. The contacts 20 are therefore mounted from the bottom of the wiring base 12 and fixed by the bottom piece 13. Finally, the composed unit is inserted into the wiring portion 16 of the case 10 and fixed together.
As described above, the unitary electrical connector is composed of wiring base 12, contacts 20, bottom piece 13 and case 10. The contacts 20 are located in a plane and bent with ends for contacting with signal source, and other ends for connecting communication wires. The layout of the contacts 20 will influence the performance of the communication.
A prior invention, referred to Taiwanese application Serial NO. 089201829, Filed Feb. 1, 2000, by the same inventor of the present invention is to improve the wiring by two metallic wires for reducing the return loss. The two wires go through the bottom piece from the top side to the bottom side and exposes with a first and a second wire portions on the top side which contact with the third and the sixth contact members when the wiring base, the contacts and the bottom piece are assembled. The two wires further go respectively under the bottom side of the bottom piece and go beyond the fourth and fifth contact members, then return to the topside as a third and a fourth wire portions to contact with the third and the sixth contact members at portions near the sharply bent ends. These by-pass loops will reduce return loss. But both ends of the wires have to be passed through the bottom piece and bent, they are hard to be fabricated.
It is therefore an object of the present invention to provide an electrical connector which can improve communication quality for higher frequency transmission and meet the requirement of Category 5e in EIA/TIA standard.
To achieve the aforesaid objects, an electrical connector capable of reducing return loss according to the present invention includes a case, a wiring base, four pairs of contacts and a bottom piece. One end of the case is formed with a wiring portion, while the other end is a socket for terminal plug of communication wires. The first pair or the third pair of contacts and the other three pairs of contacts are mounted on different sides of the bottom piece. The wiring base, the pairs of contacts and the bottom piece are composed into the case to form a unit which can solve the problem of worsen attenuation, cross talk and return loss in high frequency transmission.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.